Hammer drill

ABSTRACT

A shaft is driven by the motor of the power tool. This shaft carries a ring gear having an annular formation of teeth adapted for ratcheting engagement with an annular series of fixed teeth. When the shaft is moved inwardly of the tool housing as a result of contact of the drill bit with the work, these teeth are brought into engagement to provide a hammering action. A spindle carries the drill chuck at one of its ends; the other end of the spindle is rotatably received within a bore formed in one end of the shaft. The shaft has an external hexagonal formation at said one end thereof. The spindle has external hexagonal formations intermediate its ends. A sleeve has an internal hexagonal formation engageable with selected ones of said external formations for coupling and uncoupling the spindle and the shaft; a locking collar is mounted on the sleeve for positively locating the latter in any one of three axial positions to provide a hammering action only, a drilling action only and a combined drilling and hammering action.

United States Patent [191 Jarecki 1 Feb. 5, 1974 HAMMER DRILL [57] ABSTRACT [75] Inventor: John S. Jarecki, Villa Park, 111. A shaft is driven by the motor of the power tool. This shaft carries a ring gear having an annular formation [73] Asslgnee' S Corporation Chicago of teeth adapted for ratcheting engagement with an [22] Filed: Aug. 30, 1972 annular series of fixed teeth. When the shaft is moved inwardly of the tool housing as a result of contact of [21 1 Appl' 284738 the drill bit with the work, these teeth are brought into engagement to provide a hammering action. A spindle [52] U.S. Cl 173/48, 173/1 19, 173/123, carries the drill chuck at one of its ends; the other end 173/131 of the spindle is rotatably received within a bore [51] Int. Cl B25d 11/00, B25d 15/00 formed in one end of the shaft. The shaft has an exter- [58] Field of Search... 173/48, 95, 96, 97, 109, 110, nal hexagonal formation at said one end thereof. The

173/13 spindle has external hexagonal formations intermediate its ends. A sleeve has an internal hexagonal forma- [56] References Cited tion engageable with selected ones of said external UNITED STATES PATENTS formations for coupling and uncoupling the spindle 2223 727 12/1940 amen 173,48 and the shaft; a locking collar is mounted on the 351132l 5/1970 1.73/48 sleeve for positively locating the latter in any one of 1:162:889 12/1915 T111616 .1 173/48 three axial PSitions P"Ovide a hammering action only, a drilling action only and a combined drilling FOREIGN PATENTS OR APPLICATIONS and hammering action 810,140 8/1951 1 Germany 173/95 14 Claims, 6 Drawing Figures mamas PATENTED 51974 SHEET 2 BF 2 HAMMER DRILL BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to power tools and more particularly to power tools of the type adapted selectively to operate in a hammering mode, a drilling mode and a combined hammering and drilling mode. Such tools are used primarily for working on concrete and masonry structures.

2. The Prior Art It is known in the prior art to provide so-called rotary hammers or hammer drills which are capable of rotating a drill bit and simultaneously applying repeated axial blows to the bit. Some forms of these prior art power tools are provided with means enabling the operator of the tool to select a rotating or drilling only mode of operation as well as a hammering only mode of operation. This selective operation may be achieved by providing different working tool elements which, by reason of their amount of insertion within the tool and by reason of their external shape, cooperate with the rotating and hammering elements of the power tool to provide the selected modes of operation. In other forms of prior art power tools which do not employ different tool elements to obtain the selective modes of operation, clutches and/or complicated gearing form part of the power tool to allow the operator to select two or more modes of operation.

SUMMARY AND OBJECTS OF THE INVENTION The present invention relates to a power tool adapted selectively to operate in a hammering mode, a drilling mode and a combined hammering and drilling mode, which tool includes selector means to provide the three modes of operation independently of the type of working tool element used and without the necessity of employing complicated clutches and/or gearing.

A primary object of the present invention is the provision of a new and improved tool having unique selfcontained selector means for operating in a hammering mode, a drilling mode and a combined hammering and drilling mode.

Another object of the present invention is the provision of a power tool of the type described having a sleeve adapted to be alternately located in any one of three axial positions to provide the three modes of operation.

Still another object of the present invention is the provision of a power tool with a coupling sleeve and an associated locking collar, the locking collar being rotatable relative to the sleeve for locating the latter in any one of three axial positions to bring about the three modes of operation.

Another object of the present invention is the provision of a power tool of the type described which includes a sleeve for selectively coupling and uncoupling a shaft and a spindle, said sleeve including an abutment surface adapted to cooperate with a fixed abutment surface for preventing engagement of the hammering elements thereby to establish the drilling only mode of operation.

These and other objects and advantages of the present invention will become apparent from the following specification disclosing a preferred embodiment shown in the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial side elevation and partial vertical section of a power tool embodying the present invention;

FIG. 2 is a reduced front elevation of the power tool;

FIG. 3 is an enlarged section taken along the line 3-3 of FIG. 2;

FIG. 4 is a section taken along the line 44 of FIG.

FIG. 5 is a section taken along the line 55 of FIG. 1; and

FIG. 6 is a partial section taken along the line 6-6 of FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring primarily to FIG. 1, a power tool includes a casing or housing shell 10. It will be understood this power tool includes a suitable source of power, such as an electric or pneumatic motor, powering a drive shaft 1 1. This drive shaft has a formation of teeth at its outer end, which teeth are in meshing engagement with the teeth of a gear 12 (FIG. 3). The gear 12 is secured to the reduced-in-diameter portion 14a of a gear 14, the latter being mounted on a pin 15 having its opposite ends joumaled in bearing assemblies 16, 17. The gear 14 is in meshing engagement with a gear 18. The gear 18 is fixedly mounted on the reduced-in-diameter portion 20a of a shaft 20.

Gear 18 includes an annular series of ratcheting teeth 22 which are normally in spaced confronting relationship with a complementary annular series of ratcheting teeth 23 formed on an annular member 24. This annular member is suitably fixedly mounted and includes a central bore 25 receiving a bearing sleeve 26, which sleeve journals the shaft portion 20a. A coil spring 28 encircles the shaft portion 20a and has its opposite ends in engagement with the fixed bearing sleeve 26 and the gear 18 for normally maintaining the ratcheting teeth 22, 23 disengaged.

The juncture between the shaft 20 and its reduced-indiameter portion 20a defines an annular shoulder 20b which is abutted by one face of the gear 18. The shaft 20 is joumaled in a bearing sleeve 29, the rearward or inner end 29a-thereof constituting a stop as such end surface is abutted by the forward face of the gear 18 to limit the amount of forward axial movement of the shaft 20. Rearward or inward movement of the shaft 20 is limited or stopped by engagement of the ratcheting teeth 22, 23. The bearing sleeve 29 is suitably retained in a bore 10a formed in a housing formation 10b.

The shaft 20 includes an axially disposed blind bore 20c in which a bearing sleeve 30 is received. This bearing sleeve is tightly mounted on the reduced-indiameter cylindrical portion 32a of a spindle, generally designated 32. The spindle also includes an annular recess 32b receiving a retaining pin 34 (FIG. 6), which pin is received in a cross bore 35 extending through the shaft 20 and bearing sleeve 30.

The spindle 32 includes three external hexagonal formations 32c, 32d and 32e. The formations 32c and 32d are separated by an annular space 32f; similarly, the hexagonal formations 32d, 32e are separated by an annular space 32g. The spindle 32 mounts a drill chuck 37 of any well known construction. The drill chuck includes a frustoconical portion 37a which is separated from the spindle formation 32e by an annular space 32h.

At this time it should be mentioned that although the shaft 20 is of course cylindrical in shape along the portion thereof which is rotatably received within the bearing sleeve 29, the portion of the shaft which projects beyond the bearing sleeve 29 includes an external hexagonal formation, as indicated at 38. This hexagonal formation 38 is of the same size and shape as the hexagonal formations 32c, 32d and 32e formed on the spindle 32.

A coupling sleeve 40 includes a central hexagonal shaped opening 40a this opening is slightly larger than the hexagonal shaped formations on the spindle 32 and on the shaft 20 so as to permit axial sliding movement of the coupling sleeve 40 as will be explained hereinbelow. The sleeve 40 includes an annular space defined in part by an annular wall 40b; this wall is in spaced confronting relationship with an annular surface 42a formed on a cap 42, the latter being secured to an enlarged portion 29b of the bearing sleeve 29.

The coupling sleeve 40 includes an external annular recess 40c rotatably receiving a locking collar 44. The locking collar includes a pair of diametrically disposed, inwardly projecting pins 45 (FIG. The inner ends of these pins are received within arcuate recesses 40d formed in the locking collar 40. It will be understood that the interengagement between the pins 45 and the recesses 40d prevents relative axial movement between the coupling sleeve 40 and the locking collar 44 but permits limited rotation between these two members. In the preferred embodiment of the invention, the locking collar 44 may be rotated approximately 30 with respect to the coupling sleeve 40. Preferably a detent ball 47 is alternately received within a pair of detent recesses 44a, 44b (FIG. 4) formed in an end wall 44c of the locking collar thereby releasably to hold the latter in its two positions with respect to the coupling sleeve. A spring 48 is received within a bore 40e for yieldably urging the detent ball 47 against the inner surface of the end wall 44c.

Referring to FIG. 4, it is seen that the end wall 44c of the locking collar includes a central opening defined by six flat surfaces 44e, which surfaces are separated by six recesses 44f. When the locking collar is angularly disposed with respect to the coupling sleeve as shown in FIG. 4, the portions of the front wall 440 adjacent the flat surfaces 44e will be received in one of the annular spindle spaces 32f, 32g or 32h to prevent axial movement of the coupling sleeve. When the locking collar 44 is rotated relative to the coupling sleeve 40 so as to locate the surfaces 44e in respective parallel relation with the wall surfaces of the hexagonal formation 40a, the opening in the end wall 440 will thereupon receive the spindle hexagonal formations 32c, 32d and 32e so as to permit axial movement of the coupling sleeve 40 relative to the spindle 32.

The coupling sleeve 40 is provided with one or more rearwardly opening notches 40f adapted to receive a pin 50. This pin is received within a bore 51a of a housing piece 51. A knob 52 is secured to the pin 50 thereby to provide a convenient means for grasping the latter. Pin 50 includes an annular recess 50a receiving a detent ball 53, the latter being contained within a bore 51b and urged against the pin by means of a coil spring 54. It is apparent that the pin 50 may be withdrawn from the notch 40f by pulling the knob 52. The pin 50 is releasably held in its withdrawn position by the action of the detent ball 53 being received'in an annular space 50b.

The operation of the hammer drill of the present invention is as follows:

Assume that a suitable drill bit or working tool is secured within the chuck 37. Also assume that the coupling sleeve 40 and locking collar 44 are disposed as illustrated in FIGS. 1 and 4, i.e., the coupling sleeve is separated from the hexagonal formation 38 on the shaft 20 and locked in its forwardmost position with the portions of the collar end wall 44c adjacent the surfaces 44e received within the annular recess 32h. When the motor of the power tool is actuated, the shaft 20 will be rotated; however, this rotational force is not transmitted to the spindle 32, other than by frictional drag between the bearing sleeve 30 and the blind bore 200. Rotation of the spindle 32 may be positively prevented by locating the pin 50 in one of the notches 40f. Of course, whatever rotation is imparted to the spindle as a result of the frictional engagement between the bearing sleeve 30 and the bore 20c will be arrested upon engagement of the drill bit with the work. Accordingly, it will be appreciated by those skilled in the art that this engagement between the pin 50 and one of the notches 40f, although preferred, is not necessary.

As the tool element is brought into contact with the work, continued forward movement of the tool will result in inward axial movement of the spindle 32 and shaft 20 thereby to bring the ratcheting teeth 22, 23 into engagement with each other. The interengagement of these teeth cause a ratcheting or hammering action to provide rapid and repeated axial blows or forces to the tool element. Thus, when the coupling sleeve 40 and locking collar 44 are positioned in the manner just explained, the hammering only mode of operation is achieved.

Now, assume that the locking collar 44 is rotated relative to the coupling sleeve so as to permit axial sliding movement of the latter. Assume further that the coupling sleeve 40 is slid inwardly until the end wall 440 is in alignment with the annular space 32g whereby the locking collar may be rotated relative to the coupling sleeve. The portions of the end wall 44c adjacent the flat surfaces 44e will now be received within the annular space 32g so as to lock the coupling collar and prevent axial movement of the latter relative to the spindle. This sliding movement of the coupling sleeve 40 will cause the internal hexagonal formation 40a to slide onto the hexagonal formation 38 on the shaft 20. The pin 50 will have been withdrawn from the notch 40f prior to this axial repositioning of the coupling sleeve 40. It is now apparent that the spindle 32 will be rotated along with the shaft 20 by reason of the coupling sleeve 40. The ratcheting or hammering action will be brought about as explained above in connection with the hammering only mode of operation. Accordingly, when the coupling sleeve is positioned as just explained, the power tool will operate in a combined hammering and drilling mode.

Assume now that the locking collar 44 is again rotated relative to the coupling sleeve 40 so as to permit axial sliding movement of the latter. Assume further that the coupling sleeve is slid inwardly and the locking collar repositioned so that the portions of the end wall 44 adjacent the flat surfaces 44e are received within the spindle annular space 32f. Again, rotation from the shaft will be imparted to the spindle 32 by reason of the coupling engagement by the sleeve 40. However, rearward or inward axial movement of the shaft 20 to an extent which would bring the ratcheting teeth 22, 23 into engagement will not be permitted as the annular wall 40b on the coupling sleeve will now come into abutting engagement with the annular surface 42a after only a small amount of inward axial movement of the spindle and shaft. Accordingly, when the coupling sleeve is located as just described, the drilling only mode of operation will be achieved.

1 claim:

1. In a power tool of the type adapted selectively to operate in a hammering mode, a drilling mode and a combined hammering and drilling mode, the improvement comprising:

a. a first rotatably mounted member;

b. a second member mounted for rotation with and relative to said first member;

c. drive means connecting the motor of the tool to said second member for rotating the latter;

(1. connection means on said first member for connecting the latter to a working tool;

e. coupling means for selectively coupling and uncoupling said first and second members to and from each other;

f. hammering means independent of said coupling means and including first and second elements, said first element being connected with said drive means for rotating in unison with said second member and relative to said second element;

g. other means for selectively engaging and disengaging said first and second hammering elements;

h. whereby simultaneous hammering and drilling are achieved when said first and second elements are coupled and when said first and second elements are engaged, drilling only is achieved when said first and second members are coupled and first and second elements are disengaged, and hammering only is achieved when said first and second members are uncoupled and first and second elements are engaged.

2. The improvement according to claim 1 wherein said coupling means forms a part of said other means.

3. The improvement according to claim 1 further defined by:

a. said second member being constituted by a shaft;

b. bearing means mounting said shaft for limited axial movement;

c. biasing means urging said shaft outwardly of the housing of said power tool;

d. said shaft including an axial bore, said first member being constituted by a spindle with a portion of the latter rotatably received in said bore, the engagement between said spindle and said shaft permitting the transmission of axial forces from the former to the latter; and

e. said first and second hammering elements being in confronting relation such that they are brought into engagement with each other in response to axial v movement of said shaft inwardly of said housing.

4. The improvement according to claim 1 further defined by:

a. said second member being constituted by a shaft having a first formation at one end thereof and an axial bore opening at said one end;

b. said first member being constituted by a spindle having a cylindrical portion rotatably received within said bore and having another portion defined by a second formation; and

c. said coupling means including a sleeve mounted for movement axially of said spindle relative thereto and having a third formation engaged with only one of said first and second formations in one position of the sleeve and engaged with both of said first and second formations in another position of the sleeve.

5. The improvement according to claim 4 further defined by:

a. bearing means mounting said shaft for limited axial movement;

b. said other means including biasing means urging said shaft outwardly of the housing of said power tool;

c. said shaft including an axial bore, said spindle having a portion thereof rotatably received in said bore, the engagement between said spindle and said shaft permitting the transmission of axial forces from the former to the latter; and

d. said first and second hammering elements being in confronting relation such that they are brought into engagement with each other in response to axial movement of said shaft inwardly of said housing.

6. The improvement according to claim 1 further defined by:

a. said second member being constituted by a shaft having an external polygonal formation at one end thereof and an axial bore opening at said one end;

b. said first member being constituted by a spindle having a cylindrical portion rotatably received within said bore and having another portion defined by an external polygonal formation; and

c. said coupling means including a sleeve mounted for movement axially of said spindle relative thereto and having an internal polygonal surface engaged with only one of said external formations in one position of the sleeve and engaged with both of said external formations in another position of the sleeve.

7. The improvement according to claim 6 further defined by, a locking collar mounted for axial movement with said sleeve and for rotation relative thereto, said collar having an opening defined at least in part by a plurality of flat surfaces corresponding in number to the number of surfaces of the other of said external formations and arranged such that said opening will receive said last-mentioned formation to permit axial movement of said sleeve only when said collar is rotated relative to said sleeve for positioning said flat surfaces of the former in respective parallel relation with said surfaces of said other external formation.

8. In a power tool of the type adapted selectively to operate in a hammering mode, a drilling mode and a combined hammering and drilling mode, the improvement comprising:

a. a spindle mounted for rotation and for limited axial movement;

b. a shaft mounted for limited axial movement and for rotation with and relative to said spindle, said shaft and said spindle being engaged with each other for the transmission of axial forces;

c. drive means connecting the motor of the tool to said shaft for rotating the latter;

d. connection means on said spindle for connecting the latter to a working tool;

e. hammering means including first and second elements, said first element being connected with said shaft for rotating therewith and relative to said second element, said first and second elements being normally disengaged and being brought into engagement with each other in response to axial movement of said shaft inwardly of the housing of the power tool;

f. a first abutment surface;

g. coupling means having a second abutment surface,

said coupling means beng independent of said hammering means; and

h. means mounting said coupling means for axial movement relative to said spindle and for locating the former in any one of three positions, said coupling means engaging said shaft and said spindle and thereby coupling the same together for rotation in unison only when said coupling means occupies the first and second of its three positions, said first and second abutment surfaces being positioned for being brought into abutting engagement when said coupling means occupies said first position thereby to prevent axial movement of said shaft and the engagement of said first and second hammering elements.

9. The improvement according to claim 8 further defined by, said shaft and said spindle each having an external formation, said coupling means including a sleeve having an internal formation which engages both of said external formations when said coupling sleeve is located in said first and second positions and which engages only one of said external formations when said coupling sleeve is located in the third of its positions.

10. The improvement according to claim 9 further defined by, a locking collar mounted for movement with said coupling sleeve and for rotation relative thereto back and forth between first and second positions, said collar having an opening configured such that when said collar is in said first position the same engages one of said external formations thereby to prevent axial movement of said coupling sleeve relative to said spindle and such that when said collar is in said second position the opening therein receives said one external formation thereby to permit axial movement of said coupling sleeve relative to said spindle.

11. In a power tool of the type adapted selectively to operate in a hammering mode, a drilling mode and a combined hammering and drilling mode, the improvement comprising:

a. a spindle mounted for rotation and for limited axial movement and having an external surface formation;

b. a shaft mounted for limited axial movement and for rotation with and relative to said spindle, which shaft has an external surface formation, said shaft and said spindle being engaged with each other for the transmission of axial forces;

c. drive means connecting the motor of the tool to said shaft for rotating the latter;

d. connection means on said spindle for connecting the latter to a working tool;

e. hammering means including first and second elements, said first element being connected with said shaft for rotation therewith and relative to said second element;

f. biasing means urging said first and second hammering element apart and allowing said elements to be brought into engagement with each other in response to axial movement of said spindle inwardly of the housing of said power tool;

g. a first abutment surface;

h. a coupling sleeve having a second abutment surface and an internal surface formation;

i. a collar mounted for movement with said coupling sleeve and for rotation relative thereto so as to establish three axial positions of said coupling sleeve;

said first and second hammering elements include respective sets of ratcheting teeth.

13. In a power tool of the type adapted selectively to operate in a hammering mode, a drilling mode and a combined hammering and drilling mode, the improvement comprising:

a. a spindle mounted for rotation and for limited axial movement and having an external polygonal surface area;

b. a shaft mounted for limited axial movement and for rotation with and relative to said spindle, which shaft has an external polygonal surface area, said shaft and said spindle being engaged with each other for the transmission of axial forces;

0. drive means connecting the motor of the tool to said shaft for rotating the latter;

(1. connection means on said spindle for connecting the latter to a working tool;

e. hammering means including first and second elements, said first element being connected with said shaft for rotation therewith and relative to said second element;

f. biasing means urging said first and second hammering elements apart and allowing said elements to be brought into engagement with each other in response to axial movement of said spindle inwardly of the housing of said power tool;

g. a fixed abutment surface;

h. a coupling sleeve having an abutment surface and an internal polygonal surface area;

i. one of said external surface areas being constituted by three axially spaced-apart formations defining two annular spaces therebetween;

j. a locking collar mounted for movement with said coupling sleeve and for rotation'relative thereto back and forth between first and second positions, said locking collar having an end wall with an opening therein configured such that the same receives said formations thereby to permit axial movement of said coupling sleeve when said collar is in said first position and such that said wall is received within one or the other of said annular spaces when said collar is in said second position thereby to prevent axial movernent of said coupling sleeve;

k. said internal surface area engaging:

1. said three formations only in a first position of said coupling sleeve;

2. said external surface area and two of said formations in a second position of said coupling sleeve;

said first and second hammering elements include respective sets of ratcheting teeth. 

1. In a power tool of the type adapted selectively to operate in a hammering mode, a drilling mode and a combined hammering and drilling mode, tHe improvement comprising: a. a first rotatably mounted member; b. a second member mounted for rotation with and relative to said first member; c. drive means connecting the motor of the tool to said second member for rotating the latter; d. connection means on said first member for connecting the latter to a working tool; e. coupling means for selectively coupling and uncoupling said first and second members to and from each other; f. hammering means independent of said coupling means and including first and second elements, said first element being connected with said drive means for rotating in unison with said second member and relative to said second element; g. other means for selectively engaging and disengaging said first and second hammering elements; h. whereby simultaneous hammering and drilling are achieved when said first and second elements are coupled and when said first and second elements are engaged, drilling only is achieved when said first and second members are coupled and first and second elements are disengaged, and hammering only is achieved when said first and second members are uncoupled and first and second elements are engaged.
 2. The improvement according to claim 1 wherein said coupling means forms a part of said other means.
 2. said external surface area and two of said formations in a second position of said coupling sleeve;
 3. The improvement according to claim 1 further defined by: a. said second member being constituted by a shaft; b. bearing means mounting said shaft for limited axial movement; c. biasing means urging said shaft outwardly of the housing of said power tool; d. said shaft including an axial bore, said first member being constituted by a spindle with a portion of the latter rotatably received in said bore, the engagement between said spindle and said shaft permitting the transmission of axial forces from the former to the latter; and e. said first and second hammering elements being in confronting relation such that they are brought into engagement with each other in response to axial movement of said shaft inwardly of said housing.
 3. and said external surface area and one of said two formations in a third position of said coupling sleeve; and l. said abutment surfaces being brought into aButting engagement with each other when said coupling sleeve is in said third position thereby to prevent engagement of said first and second hammering elements.
 4. The improvement according to claim 1 further defined by: a. said second member being constituted by a shaft having a first formation at one end thereof and an axial bore opening at said one end; b. said first member being constituted by a spindle having a cylindrical portion rotatably received within said bore and having another portion defined by a second formation; and c. said coupling means including a sleeve mounted for movement axially of said spindle relative thereto and having a third formation engaged with only one of said first and second formations in one position of the sleeve and engaged with both of said first and second formations in another position of the sleeve.
 5. The improvement according to claim 4 further defined by: a. bearing means mounting said shaft for limited axial movement; b. said other means including biasing means urging said shaft outwardly of the housing of said power tool; c. said shaft including an axial bore, said spindle having a portion thereof rotatably received in said bore, the engagement between said spindle and said shaft permitting the transmission of axial forces from the former to the latter; and d. said first and second hammering elements being in confronting relation such that they are brought into engagement with each other in response to axial movement of said shaft inwardly of said housing.
 6. The improvement according to claim 1 further defined by: a. said second member being constituted by a shaft having an external polygonal formation at one end thereof and an axial bore opening at said one end; b. said first member being constituted by a spindle having a cylindrical portion rotatably received within said bore and having another portion defined by an external polygonal formation; and c. said coupling means including a sleeve mounted for movement axially of said spindle relative thereto and having an internal polygonal surface engaged with only one of said external formations in one position of the sleeve and engaged with both of said external formations in another position of the sleeve.
 7. The improvement according to claim 6 further defined by, a locking collar mounted for axial movement with said sleeve and for rotation relative thereto, said collar having an opening defined at least in part by a plurality of flat surfaces corresponding in number to the number of surfaces of the other of said external formations and arranged such that said opening will receive said last-mentioned formation to permit axial movement of said sleeve only when said collar is rotated relative to said sleeve for positioning said flat surfaces of the former in respective parallel relation with said surfaces of said other external formation.
 8. In a power tool of the type adapted selectively to operate in a hammering mode, a drilling mode and a combined hammering and drilling mode, the improvement comprising: a. a spindle mounted for rotation and for limited axial movement; b. a shaft mounted for limited axial movement and for rotation with and relative to said spindle, said shaft and said spindle being engaged with each other for the transmission of axial forces; c. drive means connecting the motor of the tool to said shaft for rotating the latter; d. connection means on said spindle for connecting the latter to a working tool; e. hammering means including first and second elements, said first element being connected with said shaft for rotating therewith and relative to said second element, said first and second elements being normally disengaged and being brought into engagement with each other in response to axial movement of said shaft inwardly of the housing of the power tool; f. a first abutment surface; g. coupling means having a second abutment surface, said coupling means beng independent of said hammering means; and h. means mounting said coupling means for axial movement relative to said spindle and for locating the former in any one of three positions, said coupling means engaging said shaft and said spindle and thereby coupling the same together for rotation in unison only when said coupling means occupies the first and second of its three positions, said first and second abutment surfaces being positioned for being brought into abutting engagement when said coupling means occupies said first position thereby to prevent axial movement of said shaft and the engagement of said first and second hammering elements.
 9. The improvement according to claim 8 further defined by, said shaft and said spindle each having an external formation, said coupling means including a sleeve having an internal formation which engages both of said external formations when said coupling sleeve is located in said first and second positions and which engages only one of said external formations when said coupling sleeve is located in the third of its positions.
 10. The improvement according to claim 9 further defined by, a locking collar mounted for movement with said coupling sleeve and for rotation relative thereto back and forth between first and second positions, said collar having an opening configured such that when said collar is in said first position the same engages one of said external formations thereby to prevent axial movement of said coupling sleeve relative to said spindle and such that when said collar is in said second position the opening therein receives said one external formation thereby to permit axial movement of said coupling sleeve relative to said spindle.
 11. In a power tool of the type adapted selectively to operate in a hammering mode, a drilling mode and a combined hammering and drilling mode, the improvement comprising: a. a spindle mounted for rotation and for limited axial movement and having an external surface formation; b. a shaft mounted for limited axial movement and for rotation with and relative to saId spindle, which shaft has an external surface formation, said shaft and said spindle being engaged with each other for the transmission of axial forces; c. drive means connecting the motor of the tool to said shaft for rotating the latter; d. connection means on said spindle for connecting the latter to a working tool; e. hammering means including first and second elements, said first element being connected with said shaft for rotation therewith and relative to said second element; f. biasing means urging said first and second hammering element apart and allowing said elements to be brought into engagement with each other in response to axial movement of said spindle inwardly of the housing of said power tool; g. a first abutment surface; h. a coupling sleeve having a second abutment surface and an internal surface formation; i. a collar mounted for movement with said coupling sleeve and for rotation relative thereto so as to establish three axial positions of said coupling sleeve; j. said internal surface formation of said coupling sleeve engaging only one of said external formations in one of said axial positions and both of said external formations in the other two of said axial positions; k. said first and second abutment surfaces being positioned for being brought into abutting engagement with each other when said coupling sleeve is in one of said two axial positions thereby to prevent engagement of said first and second hammering elements.
 12. The improvement according to claim 11 wherein said first and second hammering elements include respective sets of ratcheting teeth.
 13. In a power tool of the type adapted selectively to operate in a hammering mode, a drilling mode and a combined hammering and drilling mode, the improvement comprising: a. a spindle mounted for rotation and for limited axial movement and having an external polygonal surface area; b. a shaft mounted for limited axial movement and for rotation with and relative to said spindle, which shaft has an external polygonal surface area, said shaft and said spindle being engaged with each other for the transmission of axial forces; c. drive means connecting the motor of the tool to said shaft for rotating the latter; d. connection means on said spindle for connecting the latter to a working tool; e. hammering means including first and second elements, said first element being connected with said shaft for rotation therewith and relative to said second element; f. biasing means urging said first and second hammering elements apart and allowing said elements to be brought into engagement with each other in response to axial movement of said spindle inwardly of the housing of said power tool; g. a fixed abutment surface; h. a coupling sleeve having an abutment surface and an internal polygonal surface area; i. one of said external surface areas being constituted by three axially spaced-apart formations defining two annular spaces therebetween; j. a locking collar mounted for movement with said coupling sleeve and for rotation relative thereto back and forth between first and second positions, said locking collar having an end wall with an opening therein configured such that the same receives said formations thereby to permit axial movement of said coupling sleeve when said collar is in said first position and such that said wall is received within one or the other of said annular spaces when said collar is in said second position thereby to prevent axial movement of said coupling sleeve; k. said internal surface area engaging:
 14. The improvement according to claim 13 wherein said first and second hammering elements include respective sets of ratcheting teeth. 